Wood-eating cockroaches are not the only creatures that make their companions eat, but their motivations may be unique.
“Cannibalism is quite common in spiders,” said María José Albo, an evolutionary biologist at the University of the Republic in Uruguay. Among sexually cannibalistic spiders and insects, such as praying mantises, it is usually a larger female who eats her partner. Although on the surface it looks like a bad result for a man, it can benefit from transferring more sperm while the woman dines, said Dr. Albo.
On a less horrible note, added Dr. Albo, some male insects and spiders give their partners the so-called bridal gift: food that is sometimes made from the man’s own body. The gift may give you more time to mate – or to escape.
All of these cases involve just one companion being fed, Albo said, which makes cockroaches so unusual. “If mutual feeding of wings brings benefits to both sexes, it will be the first case of mutual feeding of gifts,” she said.
These benefits are probably not nutritional, Ms. Osaki and Dr. Kasuya wrote, because the cockroach’s wings are not fleshy. But cockroaches are likely to benefit from losing their wings, because the wings are heavy when they live in tight spaces. The wings can also collect mold or mites, the authors wrote.
“It makes sense that there is an advantage to getting rid of your wings if you’re never going to fly again,” said Allen J. Moore, an evolutionary biologist at the University of Georgia. Some other insects that live underground or inside the wood also lose their wings after mating, such as termites, close relatives that Dr. Moore called “sophisticated cockroaches”.
But these insects need to lose their wings on their own. “This mutual aid is really unique,” he said.